But while just about every major car company has a self-driving car they're showing off (here's BMW's latest video) and intentions to add semi-autonomous features to new cars in the near future, the question remains: when will we self-driving cars actually be on the roads in significant numbers?

The latest to try to answer that question is the research company IHS. In a new study, the company predicts that globally there will be 54 million self-driving cars on the road by 2035, with annual sales rising from 230,000 in 2025 to 11.8 million in 2035. By 2050, the company says, "nearly all of the vehicles in use are likely to be self-driving cars or self-driving commercial vehicles."

What will the driverless technology features add to the price of the car? IHS says that driverless technology will add between $7,000 and $10,000 to a car’s sticker price in 2025. That premium is expected to drop to $5,000 in 2030 and $3,000 in 2035.

Of course, there are still plenty of hurdles before reaching any of these milestones, decades away. But the biggest one likely won't be technology.

"The only thing that is stopping us is the legal stuff," Patrick Heinemann, an engineer of advanced driver assistance systems for Audi AG, told the Associated Press.

In the United States, there are numerous states -- from Florida to California -- that are trying to make sure they are ahead of the curve with driverless car laws already on the books. But a new study from RAND Corporation looking at the benefits and challenges of self-driving cars says that these laws could lead to a "patchwork of conflicting regulatory requirements that vary from state to state, which could undermine potential benefits."

For policymakers, RAND has four suggestions:

Avoid passing regulations prematurely while the technology is still evolving.

Update distracted-driving laws.

Clarify who will own the data generated by this technology and how it will be used, and address privacy concerns

Regulations and liability rules should be designed by comparing the performance of autonomous vehicles to that of average human drivers and the long-term benefits of the technology should be incorporated into determinations of liability.

But once those are sorted out, RAND believes the benefits of self-driving cars -- from increased safety to increased fuel economy -- will outweigh the challenges.